Method and apparatus for transmitting indication in wireless communication system

ABSTRACT

A method and apparatus for transmitting an indication in a wireless communication system is provided. A relay node (RN) transmits an indication which indicates that the RN is either a fixed relay node or a mobile relay node, and receives initial parameters from an operation, administration, and maintenance (OAM) according on the indication. If the RN is the mobile relay node, the initial parameters includes a list of donor eNodeB (DeNB) cells at a trajectory of the RN.

This Application is a 35 U.S.C. § 371 National Stage entry ofInternational Application No. PCT/KR2013/005637, filed Jun. 26, 2013,which claims benefit of Provisional Application No. 61/665,869 filedJun. 28, 2012, both of which are incorporated by reference in theirentirety herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to wireless communication, and moreparticularly, to a method and apparatus for transmitting an indicationin a wireless communication system.

Related Art

Universal mobile telecommunications system (UMTS) is a 3rd generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3GPP LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

FIG. 1 shows network structure of an evolved universal mobiletelecommunication system (E-UMTS). The E-UMTS may be also referred to asan LTE system. The communication network is widely deployed to provide avariety of communication services such as voice over internet protocol(VoIP) through IMS and packet data.

As illustrated in FIG. 1, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an evolved packet core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNB) 20, and a plurality of user equipment (UE) 10. Oneor more E-UTRAN mobility management entity (MME)/system architectureevolution (SAE) gateways (S-GW) 30 may be positioned at the end of thenetwork and connected to an external network.

As used herein, “downlink” refers to communication from eNB 20 to UE 10,and “uplink” refers to communication from the UE to an eNB. UE 10 refersto communication equipment carried by a user and may be also referred toas a mobile station (MS), a user terminal (UT), a subscriber station(SS) or a wireless device.

An eNB 20 provides end points of a user plane and a control plane to theUE 10. MME/S-GW 30 provides an end point of a session and mobilitymanagement function for UE 10. The eNB and MME/S-GW may be connected viaan S1 interface.

The eNB 20 is generally a fixed station that communicates with a UE 10,and may also be referred to as a base station (BS) or an access point.One eNB 20 may be deployed per cell. An interface for transmitting usertraffic or control traffic may be used between eNBs 20.

The MME provides various functions including non-access stratum (NAS)signaling to eNBs 20, NAS signaling security, access stratum (AS)security control, Inter core network (CN) node signaling for mobilitybetween 3GPP access networks, Idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), packet data network (PDN)GW and serving GW selection, MME selection for handovers with MMEchange, serving GPRS support node (SGSN) selection for handovers to 2Gor 3G 3GPP access networks, roaming, authentication, bearer managementfunctions including dedicated bearer establishment, support for publicwarning system (PWS) (which includes earthquake and tsunami warningsystem (ETWS) and commercial mobile alert system (CMAS)) messagetransmission. The S-GW host provides assorted functions includingper-user based packet filtering (by e.g. deep packet inspection), lawfulinterception, UE internet protocol (IP) address allocation, transportlevel packet marking in the downlink, UL and DL service level charging,gating and rate enforcement, DL rate enforcement based on APN-AMBR. Forclarity MME/S-GW 30 will be referred to herein simply as a “gateway,”but it is understood that this entity includes both an MME and an SAEgateway.

A plurality of nodes may be connected between eNB 20 and gateway 30 viathe S1 interface. The eNBs 20 may be connected to each other via an X2interface and neighboring eNBs may have a meshed network structure thathas the X2 interface.

FIG. 2 shows architecture of a typical E-UTRAN and a typical EPC.

As illustrated, eNB 20 may perform functions of selection for gateway30, routing toward the gateway during a radio resource control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of broadcast channel (BCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE_IDLE state management,ciphering of the user plane, SAE bearer control, and ciphering andintegrity protection of NAS signaling.

FIG. 3 shows a user-plane protocol and a control-plane protocol stackfor the E-UMTS.

FIG. 3(a) is block diagram depicting the user-plane protocol, and FIG.3(b) is block diagram depicting the control-plane protocol. Asillustrated, the protocol layers may be divided into a first layer (L1),a second layer (L2) and a third layer (L3) based upon the three lowerlayers of an open system interconnection (OSI) standard model that iswell known in the art of communication systems.

The physical layer, the L1, provides an information transmission serviceto an upper layer by using a physical channel. The physical layer isconnected with a medium access control (MAC) layer located at a higherlevel through a transport channel, and data between the MAC layer andthe physical layer is transferred via the transport channel. Betweendifferent physical layers, namely, between physical layers of atransmission side and a reception side, data is transferred via thephysical channel.

The MAC layer of the L2 provides services to a radio link control (RLC)layer (which is a higher layer) via a logical channel. The RLC layer ofthe L2 supports the transmission of data with reliability. It should benoted that the RLC layer illustrated in FIGS. 3(a) and 3(b) is depictedbecause if the RLC functions are implemented in and performed by the MAClayer, the RLC layer itself is not required. A packet data convergenceprotocol (PDCP) layer of the L2 performs a header compression functionthat reduces unnecessary control information such that data beingtransmitted by employing IP packets, such as IPv4 or IPv6, can beefficiently sent over a radio (wireless) interface that has a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the lowest portion ofthe L3 is only defined in the control plane and controls logicalchannels, transport channels and the physical channels in relation tothe configuration, reconfiguration, and release of the radio bearers(RBs). Here, the RB signifies a service provided by the L2 for datatransmission between the terminal and the UTRAN.

As illustrated in FIG. 3(a), the RLC and MAC layers (terminated in aneNB 20 on the network side) may perform functions such as scheduling,automatic repeat request (ARQ), and hybrid automatic repeat request(HARQ). The PDCP layer (terminated in eNB 20 on the network side) mayperform the user plane functions such as header compression, integrityprotection, and ciphering.

As illustrated in FIG. 3(b), the RLC and MAC layers (terminated in aneNodeB 20 on the network side) perform the same functions for thecontrol plane. As illustrated, the RRC layer (terminated in an eNB 20 onthe network side) may perform functions such as broadcasting, paging,RRC connection management, RB control, mobility functions, and UEmeasurement reporting and controlling. The NAS control protocol(terminated in the MME of gateway 30 on the network side) may performfunctions such as a SAE bearer management, authentication, LTE_IDLEmobility handling, paging origination in LTE_IDLE, and security controlfor the signaling between the gateway and UE 10.

The RRC state may be divided into two different states such as aRRC_IDLE and a RRC_CONNECTED. In RRC_IDLE state, the UE 10 may receivebroadcasts of system information and paging information while the UEspecifies a discontinuous reception (DRX) configured by NAS, and the UEhas been allocated an identification (ID) which uniquely identifies theUE in a tracking area and may perform PLMN selection and cellre-selection. Also, in RRC_IDLE state, no RRC context is stored in theeNB.

In RRC_CONNECTED state, the UE 10 has an E-UTRAN RRC connection and acontext in the E-UTRAN, such that transmitting and/or receiving datato/from the network (eNB) becomes possible. Also, the UE 10 can reportchannel quality information and feedback information to the eNB.

In RRC_CONNECTED state, the E-UTRAN knows the cell to which the UE 10belongs. Therefore, the network can transmit and/or receive data to/fromUE 10, the network can control mobility (handover and inter-radio accesstechnologies (RAT) cell change order to GSM EDGE radio access network(GERAN) with network assisted cell change (NACC)) of the UE, and thenetwork can perform cell measurements for a neighboring cell.

In RRC_IDLE state, the UE 10 specifies the paging DRX cycle.Specifically, the UE 10 monitors a paging signal at a specific pagingoccasion of every UE specific paging DRX cycle.

The paging occasion is a time interval during which a paging signal istransmitted. The UE 10 has its own paging occasion.

A paging message is transmitted over all cells belonging to the sametracking area. If the UE 10 moves from one tracking area to anothertracking area, the UE will send a tracking area update message to thenetwork to update its location.

FIG. 4 shows an example of structure of a physical channel.

The physical channel transfers signaling and data between layer L1 of aUE and eNB. As illustrated in FIG. 4, the physical channel transfers thesignaling and data with a radio resource, which consists of one or moresub-carriers in frequency and one more symbols in time.

One sub-frame, which is 1 ms in length, consists of several symbols. Theparticular symbol(s) of the sub-frame, such as the first symbol of thesub-frame, can be used for downlink control channel (PDCCH). PDCCHscarry dynamic allocated resources, such as PRBs and modulation andcoding scheme (MCS).

A transport channel transfers signaling and data between the L1 and MAClayers. A physical channel is mapped to a transport channel.

Downlink transport channel types include a broadcast channel (BCH), adownlink shared channel (DL-SCH), a paging channel (PCH) and a multicastchannel (MCH). The BCH is used for transmitting system information. TheDL-SCH supports HARQ, dynamic link adaptation by varying the modulation,coding and transmit power, and both dynamic and semi-static resourceallocation. The DL-SCH also may enable broadcast in the entire cell andthe use of beamforming. The PCH is used for paging a UE. The MCH is usedfor multicast or broadcast service transmission.

Uplink transport channel types include an uplink shared channel (UL-SCH)and random access channel(s) (RACH). The UL-SCH supports HARQ anddynamic link adaptation by varying the transmit power and potentiallymodulation and coding. The UL-SCH also may enable the use ofbeamforming. The RACH is normally used for initial access to a cell.

The MAC sublayer provides data transfer services on logical channels. Aset of logical channel types is defined for different data transferservices offered by MAC. Each logical channel type is defined accordingto the type of information transferred.

Logical channels are generally classified into two groups. The twogroups are control channels for the transfer of control planeinformation and traffic channels for the transfer of user planeinformation.

Control channels are used for transfer of control plane informationonly. The control channels provided by MAC include a broadcast controlchannel (BCCH), a paging control channel (PCCH), a common controlchannel (CCCH), a multicast control channel (MCCH) and a dedicatedcontrol channel (DCCH). The BCCH is a downlink channel for broadcastingsystem control information. The PCCH is a downlink channel thattransfers paging information and is used when the network does not knowthe location cell of a UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting MBMS control information from the networkto a UE. The DCCH is a point-to-point bi-directional channel used by UEshaving an RRC connection that transmits dedicated control informationbetween a UE and the network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by MAC include a dedicated trafficchannel (DTCH) and a multicast traffic channel (MTCH). The DTCH is apoint-to-point channel, dedicated to one UE for the transfer of userinformation and can exist in both uplink and downlink. The MTCH is apoint-to-multipoint downlink channel for transmitting traffic data fromthe network to the UE.

Uplink connections between logical channels and transport channelsinclude a DCCH that can be mapped to UL-SCH, a DTCH that can be mappedto UL-SCH and a CC CH that can be mapped to UL-SCH. Downlink connectionsbetween logical channels and transport channels include a BCCH that canbe mapped to BCH or DL-SCH, a PCCH that can be mapped to PCH, a DCCHthat can be mapped to DL-SCH, and a DTCH that can be mapped to DL-SCH, aMCCH that can be mapped to MCH, and a MTCH that can be mapped to MCH.

3GPP LTE-A may supports relaying by having a relay node (RN) wirelesslyconnect to an eNB serving the RN. It may be referred to paragraph 4.7 of3rd generation partnership project (3GPP) TS 36.300 V10.2.0 (2010-12).

FIG. 5 shows an objective of relay.

Referring to FIG. 5, a relay node (RN) wirelessly communicates with aneNB supporting relay, and thus can support capacity assistance of ashadow region or coverage extension through a service for UEs located ina cell boundary region and outside the boundary region. The eNB servingthe RN may be referred as a donor eNB (DeNB). The DeNB requires severaladditional functions for supporting relay. When there is an access ofthe relay node, the DeNB can perform a reconfiguration task to provideinformation required for relay and system information through dedicatedsignaling. The DeNB and the RN may be connected via a modified versionof the E-UTRA radio interface. The modified version may be referred as aUn interface.

The RN may support eNB functionality. It means that the RN terminatesthe radio protocols of the E-UTRA radio interface, and S1 and X2interfaces. In addition to the eNB functionality, the RN may alsosupport a subset of UE functionality, e.g., a physical layer, layer-2,RRC, and NAS functionality, in order to wirelessly connect to the DeNB.That is, the relay node can operate as a relay-type UE with respect tothe DeNB, and can operate as an eNB with respect to a served UE.

FIG. 6 shows an overall E-UTRAN architecture supporting relay nodes.

Referring to FIG. 6, the LTE-A network includes an E-UTRAN, an EPC andone or more user equipment (not described). The E-UTRAN may include oneor more relay node (RN) 50, one or more DeNB 60, one or more eNB 61 anda plurality of UE may be located in one cell. One or more E-UTRANMME/S-GW 70 may be positioned at the end of the network and connected toan external network.

As used herein, “downlink” refers to communication from the eNB 61 tothe UE, from the DeNB 60 to the UE or from the RN 50 to the UE, and“uplink” refers to communication from the UE to the eNB 61, from the UEto the DeNB 60 or from the UE to the RN 50. The UE refers tocommunication equipment carried by a user and may be also referred to asa mobile station (MS), a user terminal (UT), a subscriber station (SS)or a wireless device.

The eNB 61 and the DeNB 60 provide end points of a user plane and acontrol plane to the UE. The MME/S-GW 70 provides an end point of asession and mobility management function for UE. The eNB 61 and theMME/S-GW 70 may be connected via an S1 interface. The DeNB 60 andMME/SAE gateway 70 may be connected via an S1 interface. The eNBs 61 maybe connected to each other via an X2 interface and neighboring eNBs mayhave a meshed network structure that has the X2 interface. The eNB 61and the DeNB 60 may be connected to each other via an X2 interface.

The RN 50 may be wirelessly connected to the DeNB 60 via a modifiedversion of the E-UTRA radio interface being called the Un interface.That is, the RN 50 may be served by the DeNB 60. The RN 50 may supportthe eNB functionality which means that it terminates the S1 and X2interfaces. Functionality defined for the eNB 61 or the DeNB 60, e.g.radio network layer (RNL) and transport network layer (TNL), may alsoapply to RNs 50. In addition to the eNB functionality, the RN 50 mayalso support a subset of the UE functionality, e.g. physical layer,layer-2, RRC, and NAS functionality, in order to wirelessly connect tothe DeNB 60.

The RN 50 may terminate the S1, X2 and Un interfaces. The DeNB 60 mayprovide S1 and X2 proxy functionality between the RN 50 and othernetwork nodes (other eNBs, MMEs and S-GWs). The S1 and X2 proxyfunctionality may include passing UE-dedicated S1 and X2 signalingmessages as well as GTP data packets between the S1 and X2 interfacesassociated with the RN 50 and the S1 and X2 interfaces associated withother network nodes. Due to the proxy functionality, the DeNB 60 appearsas an MME (for S1) and an eNB (for X2) to the RN 50.

The DeNB 60 may also embed and provides the S-GW/P-GW-like functionsneeded for the RN operation. This includes creating a session for the RN50 and managing EPS bearers for the RN 50, as well as terminating theS11 interface towards the MME serving the RN 50.

The RN 50 and the DeNB 60 may also perform mapping of signaling and datapackets onto EPS bearers that are setup for the RN. The mapping may bebased on existing QoS mechanisms defined for the UE and the P-GW.

The relay node may be classified to a fixed relay node and a mobilerelay node. The mobile relay node may be applied to the 3GPP LTE rel-11.One of the possible deployment scenarios of mobile relay node is highspeed public transportation, e.g. a high speed railway. That is, themobile relay node may be put on the top of a high speed train. Hence, itis easily expected that the provision of various good quality servicestowards the users on a high speed public transportation will beimportant. Meanwhile, the service requirements offered by the fixedrelay node seem to be different from those offered by the mobile relaynode. So, there might be a few of considerations that should be resolvedin the mobile relay node. The solutions to resolve these considerationsfor mobile relay node may have impacts on a radio access network (RAN).

FIG. 7 shows an example of deployments scenario of a mobile relay nodeat a high speed train.

Referring to FIG. 7, a mobile relay node is installed in a high speedtrain. Coverage of the mobile relay node may correspond to the entiretyof the high speed train or each of cars constituting the high speedtrain. The mobile relay node can communicate with UEs in the high speedtrain through an access link. At present, the mobile relay node is incoverage of an eNB1 supporting relay. The mobile relay node cancommunicate with the eNB1 through a backhaul link. When the high speedtrain moves, the mobile relay node may enter coverage of an eNB2supporting relay. Accordingly, the mobile relay node can be handed overfrom the eNB1 to the eNB2.

It is required that a method to support both a fixed relay node and amobile relay node reliably.

SUMMARY OF THE INVENTION

The present invention provides a method for transmitting an indicationin a wireless communication system. The present invention provides amethod for transmitting an indication which indicates that a relay nodeis either a fixed relay node or a mobile relay node.

In an aspect, a method for transmitting, by a relay node (RN), anindication in a wireless communication system is provided. The methodincludes transmitting an indication which indicates that the RN iseither a fixed relay node or a mobile relay node, and receiving initialparameters from an operation, administration, and maintenance (OAM)according on the indication.

The initial parameters may include a list of donor eNodeB (DeNB) cellsat a trajectory of the RN if the RN is the mobile relay node. The RN maybe deployed at a high-speed train.

In another aspect, a relay node (RN) in a wireless communication systemis provided. The RN includes a radio frequency (RF) unit fortransmitting or receiving a radio signal, and a processor coupled to theRF unit and configured for transmitting an indication which indicatesthat the RN is either a fixed relay node or a mobile relay node, andreceiving initial parameters from an operation, administration, andmaintenance (OAM) according on the indication.

When a relay node is a mobile relay node, the relay node does not haveto perform a user equipment (UE) attach procedure frequently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows network structure of an evolved universal mobiletelecommunication system (E-UMTS).

FIG. 2 shows architecture of a typical E-UTRAN and a typical EPC.

FIGS. 3a and 3b show a user-plane protocol and a control-plane protocolstack for the E-UMTS.

FIG. 4 shows an example of structure of a physical channel.

FIG. 5 shows an objective of relay.

FIG. 6 shows an overall E-UTRAN architecture supporting relay nodes.

FIG. 7 shows an example of deployments scenario of a mobile relay nodeat a high speed train.

FIG. 8 shows a simplified version of an attach procedure for a relaynode (RN).

FIG. 9 shows a simplified version of a DeNB-initiated beareractivation/modification procedure.

FIG. 10 shows a simplified version of a startup procedure for an RN.

FIG. 11 shows a simplified version of a detach procedure for a relaynode operation in case no UE is connected to a RN.

FIG. 12 shows an example of RN OAM architecture.

FIG. 13 shows an example of a method for transmitting an indicationaccording to an embodiment of the present invention.

FIG. 14 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is an evolution of IEEE 802.16e, and provides backwardcompatibility with an IEEE 802.16-based system. The UTRA is a part of auniversal mobile telecommunication system (UMTS). 3rd generationpartnership project (3GPP) long term evolution (LTE) is a part of anevolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA indownlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is anevolution of the 3GPP LTE.

For clarity, the following description will focus on the LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 8 shows a simplified version of an attach procedure for a relaynode (RN).

1. An RN and a donor eNodeB (eNB) setup a radio resource control (RRC)connection.

2a. The RN and a mobility management entity (MME) performs non-accessstratum (NAS) attach, authentication, security, etc.

2b. The MME and a home subscriber server (HSS) perform authentication,security, etc.

3. The DeNB and the MME create a GPRS tunneling protocol control plane(GTP-C) session.

4a. The RN and the DeNB reconfigure the RRC connection.

4b. The DeNB and the MME setup an S1 context.

This procedure is similar to a normal user equipment (UE) attachprocedure. The DeNB may be aware of which MMEs support RN functionalityvia an S1 setup response message earlier received from the MMEs. The RNmay transmit an RN indication to the DeNB during RRC connectionestablishment. After receiving the RN indication from the RN, the DeNBmay transmit the RN indication and an Internet protocol (IP) address ofthe S-GW/P-GW function embedded in the DeNB, within an initial UEmessage, to the MME supporting RN functionality. The MME may selectS-GW/P-GW for the RN based on the IP address included in the initial UEmessage. During the attach procedure, the EPC checks if the RN isauthorized for relay operation. Only if the RN is authorized, the EPCaccepts the attach procedure and sets up a context with the DeNB.Otherwise the EPC rejects the attach procedure. The RN may bepreconfigured with information about which cells (DeNBs) it is allowedto access.

FIG. 9 shows a simplified version of a DeNB-initiated beareractivation/modification procedure.

1. A DeNB transmits a GTP-C create/update bearer request message to anMME.

2. The MME transmits an S1-AP bearer setup/modify request message to theDeNB.

3. An RN and the DeNB reconfigure an RRC connection.

4. The DeNB transmits an S1-AP bearer setup/modify response message tothe MME.

5a/5b. Direct transfer is performed from the RN to the DeNB, and fromthe DeNB to the MME.

6. The MME transmits a GTP-C create/update bearer response message tothe DeNB.

This procedure may be used by the DeNB to change the EPS bearerallocation for the RN. This procedure is the same as a normalnetwork-initiated bearer activation/modification procedure.

FIG. 10 shows a simplified version of a startup procedure for an RN.

This procedure is based on a normal UE attach procedure and it consistsof the following two phases. This procedure may be defined for a fixedrelay node or a mobile relay node.

1) Phase I: Attach for RN Preconfiguration.

The RN attaches to an E-UTRAN/EPC as a UE at power-up and retrievesinitial configuration parameters, including a list of DeNB cells, froman RN operation, administration, and maintenance (OAM). After thisoperation is completed, the RN detaches from the network as a UE andtriggers a phase II. The MME performs the S-GW and P-GW selection forthe RN as a normal UE.

2) Phase II: Attach for RN Operation.

The RN attaches as a relay for setup and operations. The RN connects toa DeNB selected from the list acquired during the phase I to start relayoperations. For this purpose, a normal RN attach procedure described inFIG. 8 may be applied. In this case, the RN may provide an RN indicatorto the DeNB during an RRC connection establishment. Also, the MMEprovides an RN support indication to the DeNB at S1 setup. After theDeNB initiates setup of bearer for S1/X2, the RN initiates a setup of S1and X2 associations with the DeNB. In addition, the DeNB may initiate anRN reconfiguration procedure via RRC signaling for RN-specificparameters.

After the S1 setup, the DeNB performs an S1 eNB configuration updateprocedure, if configuration data for the DeNB is updated due to the RNattach. After the X2 setup, the DeNB performs an X2 eNB configurationupdate procedure to update the cell information.

In this phase the RN cells' evolved cell global identifiers (ECGIs) areconfigured the RN OAM.

FIG. 11 shows a simplified version of a detach procedure for a relaynode operation in case no UE is connected to a RN. The detach procedureis the same as a normal UE detach procedure. The DeNB performs the X2eNB configuration update procedure to update the cell information. TheDeNB performs the S1 eNB configuration update procedure, ifconfiguration data for the DeNB is updated due to the RN detach.

The X2 eNB configuration update procedure described above may be used bythe DeNB to also transfer application level configuration data of asingle neighboring eNB to the RN. Upon reception of an eNB configurationupdate message, if the served cells contained in the eNB configurationupdate message belong to the neighbor eNB rather than the DeNB, the RNshall regard the X2 interface between the DeNB and the neighbor eNB asavailable. The RN will update an X2 availability, the corresponding GUgroup ID and other information of the neighbor eNB according to the eNBconfiguration update message.

FIG. 12 shows an example of RN OAM architecture.

Each RN may transmit alarms and traffic counter information to its OAMsystem, from which it receives commands, configuration data and softwaredownloads (e.g. for equipment software upgrades). This transportconnection between each RN and its OAM, using IP, may be provided by theDeNB. RN OAM traffic is transported over the Un interface, and it sharesresources with the rest of the traffic, including UEs attached to theDeNB. The secure connection between the RN and its OAM may be direct orhop-by-hop, i.e. involving intermediate hops trusted by the operator forthis purpose. The RN OAM architecture described in FIG. 12 refers tonormal operating conditions for the RN, i.e. after the initial start-upphase has been completed.

If a network supports both a fixed relay node and a mobile relay node,the startup procedure for the RN, described in FIG. 10, may be appliedfor the mobile relay node. As the mobile relay node moves, a DeNB whichserves the mobile relay node may be changed frequently. For this,according to the conventional art, the mobile relay node needs toperform the UE attach procedure described in FIG. 10 (Phase I) toreceive a list of DeNB cells to be changed before the DeNB which servesthe mobile relay node is changed. For example, a mobile relay node, puton the top of a high speed train, should perform the UE attach procedurefrequently as the change of the DeNB is highly probable, thus, themobile relay node needs to obtain a list of DeNB cells from an RN OAMfrequently.

In addition, in case that the mobile relay node attaches to a new DeNBas the mobile relay node moves, the mobile relay node should perform adetach procedure from a previous DeNB as described in FIG. 11. However,if the mobile relay node performs the detach procedure, an EPS sessionof the mobile relay node and network/radio resources allocated to abearer should be released, and therefore, services provided to UEs,attached to the mobile relay node, may be interrupted.

To solve the problem described above, a method for transmitting anindication according to an embodiment of the present invention may beproposed.

FIG. 13 shows an example of a method for transmitting an indicationaccording to an embodiment of the present invention.

In a network supporting both a fixed relay node and a mobile relay node,after completion of attaching as a regular UE for initial configuration,at step S100, an RN transmits an indication which indicates that the RNis either a fixed relay node or a mobile relay node, to an OAM. Onreceiving the indication from the RN, the OAM may identify a type of thecurrently attached RN.

At step S110, the OAM transmits initial parameters to the RN. In thiscase, as the OAM know the type of the attached RN according to theindication received from the RN, the OAM may provide differentinformation respectively according to the type of the RN. If the RN is afixed relay node, the OAM may provide a list of DeNB cells asconventional arts. If the RN is a mobile relay node, the OAM may providea list of DeNB cells deployed at trajectory of the relay node becausedestination and trajectory of the RN is pre-determined when the relaynode is deployed at a high-speed train.

According to embodiments of the present invention, when a relay node isa mobile relay node, the relay node does not have to perform a UE attachprocedure to receive a list of DeNB cells. The relay node may know alist of DeNB cells at trajectory of the relay node in advance, and therelay node may perform a handover procedure efficiently while movingfast.

FIG. 14 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

A relay node 800 includes a processor 810, a memory 820, and an RF(radio frequency) unit 830. The processor 810 may be configured toimplement proposed functions, procedures, and/or methods in thisdescription. Layers of the radio interface protocol may be implementedin the processor 810. The memory 820 is operatively coupled with theprocessor 810 and stores a variety of information to operate theprocessor 810. The RF unit 830 is operatively coupled with the processor810, and transmits and/or receives a radio signal.

An OAM 900 may include a processor 910, a memory 920 and a RF unit 930.The processor 910 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 910. Thememory 920 is operatively coupled with the processor 910 and stores avariety of information to operate the processor 910. The RF unit 930 isoperatively coupled with the processor 910, and transmits and/orreceives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The RF units 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method for transmitting, by a relay node (RN),an indication in a wireless communication system, the method comprising:transmitting, by the RN, the indication which indicates that the RN iseither a fixed relay node or a mobile relay node, to an operation,administration, and maintenance (OAM); and if the indication indicatesthat the RN is the mobile relay node, and if trajectory of the RN ispre-determined, receiving, by the RN, a list of donor eNodeB (DeNB)cells for the mobile relay node, from the OAM, wherein the DeNB cellsfor the mobile relay node are cells deployed at the pre-determinedtrajectory of the RN, if the indication indicates that the RN is thefixed relay node, receiving, by the RN, a list of DeNB cells for thefixed relay node, from the OAM, wherein the DeNB cells for the fixedrelay node are cells deployed at a neighbor of the RN, wherein themobile relay node is deployed on a vehicle which moves along thepre-determined trajectory.
 2. The method of claim 1, wherein the mobilerelay node is deployed on a train.
 3. The method of claim 1, furthercomprising attaching as a user equipment (UE) for initial configurationbefore transmitting the indication.
 4. A relay node (RN) in a wirelesscommunication system, the RN comprising: a radio frequency (RF) unit fortransmitting or receiving a radio signal; and a processor, coupled tothe RF unit, that: controls the RF unit to transmit an indication whichindicates that the RN is either a fixed relay node or a mobile relaynode, to an operation, administration, and maintenance (OAM); and if theindication indicates that the RN is the mobile relay node, and iftrajectory of the RN is pre-determined, controls the RF unit to receivea list of donor eNodeB (DeNB) cells for the mobile relay node, from theOAM, wherein the DeNB cells for the mobile relay node are cells deployedat the pre-determined trajectory of the RN, if the indication indicatesthat the RN is the fixed relay node, controls the RF unit to receive alist of DeNB cells for the fixed relay node, from the OAM, wherein theDeNB cells for the fixed relay node are cells deployed at a neighbor ofthe RN, wherein the mobile relay node is deployed on a vehicle whichmoves along the pre-determined trajectory.
 5. The RN of claim 4, whereinthe mobile relay node is deployed on a train.
 6. The RN of claim 4,wherein the processor further attaches as a user equipment (UE) forinitial configuration before transmitting the indication.